The present invention relates to paints and pigments with improved corrosion inhibition properties.
Mankind has long sought to protect metals, in particular ferrous metals, from corrosion. A variety of more or less effective ways to provide such protection have been discovered, many of which involve coating the metal structure with a composition which includes a metal or metal compound. Often these metals are toxic or otherwise environmentally harmful. In order to provide a more "environmentally friendly" product, certain compositions have been used which avoid or minimize the use of toxic metals or their compounds. Unfortunately many of these environmentally friendly coatings are less effective at preventing corrosion than are the traditional anti-corrosion materials.
U.S. Pat. No. 4,629,753, Quinn, Dec. 16, 1986, discloses non-asphaltic, non-mastic type, water dispersed rust inhibiting coating compositions comprising in admixture a film-forming organic polymer and a non-Newtonian colloidal disperse system which contains solid metal containing colloidal particles.
U.S. Pat. No. 4,153,465, Hund et al., May 8, 1979, discloses an anticorrosion pigment suited for paints and lacquers consisting of CaZn.sub.2 (PO.sub.4).sub.2.2H.sub.2 O crystallizing in the Scholzite lattice. The material is prepared by precipitating an aqueous solution containing Ca.sup.2+ and Zn.sup.2+ cations. It may be used in usual binders for lacquers.
U.S. Pat. No. 4,346,184, Drake, Aug. 24, 1982, discloses a water soluble zinc oxide/phosphorous pentoxide/alumina glass which, when in contact with water, releases ions which inhibit corrosion of adjacent glass surfaces. The glass may be dispersed in a resin carrier to form a paint.
U.S. Pat. No. 3,565,843, Kassinger et al., Feb. 23, 1971, discloses an organic rust inhibiting composition of (1) a gelled overbased alkaline earth metal sulfonate (such as calcium petroleum sulfonate treated with an aqueous ammonia solution) (2) a coating material, and (3) a hydrocarbon solvent. The composition is improved over conventional asphalt based "undercoatings."
U.S. Pat. No. 2,695,910, Asseff et al., Nov. 30, 1954, discloses methods of preparation of superbased salts, i.e., metal complexes which contain substantially more metal in combination than is found in complexes prepared by the prior art. The superbased salts can be employed in lubricants and i.a. as rust inhibition compositions.
It has now been found that certain combinations of salts of organic acids with other metal-containing corrosion inhibitors lead to improved corrosion protection, so that even the environmentally friendly compositions can provide excellent corrosion protection.